By 'open-ish' I meant that the main platform it ships with is Steam OS and that's what the majority of users will interact with, I wasn't referring to a walled garden type of atmosphere, I should have been clearer, apologies for that.
I still contend however that both will face a BOM issues hardware wise, which software will have to factor in later. Nintendo can afford to take deeper cuts, but they always try to avoid this, 'lateral thinking with withered technology' and all that. SD has the convenience of targeting a more 'hardcore' base of users who will likely pay more of a premium for their hardware, Nintendo has a much wider demographic target and thus will try to squeeze into that Goldilocks price for a blue ocean demographic. SD doesn't really have that problem. For now anyway, I expect Valve will eventually try to cater to wider demographics with tiered hardware, or just keep targeting their current demographics. Who knows where and how Valve plans to expand the platform and who knows how and where Nintendo will expand theirs as well.